1. Field of the Invention
This invention relates to the field of internal combustion engines in general, and in particular to such engines having adjustably timed valves or ports, the control of which will conserve fuel.
2. Prior Art
The internal combustion engine art has for many years been attempting to solve the problem of fuel being wasted during low speed conditions due to the non-adjustment capabilities of the engine upon completion of high speed requirements. Until recently, only a partial solution has been provided by automatic spark advance in the distributor. Consequently, numerous approaches have been devised to provide an adjustment mechanism so that the engine will use less fuel during these conditions. Typically, this has been accomplished by disabling selected cylinders, which ordinarily involves the interruption of the fuel flow. Some have gone as far as teaching the removal of several portions of the cylinder such that even during heavy load operation these cylinders are still ineffective, for example U.S. Pat. Nos. 3,874,358-Crower, 3,945,367-Turner and 4,070,971-Studebaker. In each of these patent the intake and exhaust valves of the disabled cylinders are purposely maintained in a continuously closed orientation, providing an amount of vacuum and compression during the operation of the engine. To overcome this problem U.S. Pat. No. 3,874,358 teaches the substitution of pistons having passages therein to prevent these effects. U.S. Pat. No. 3,945,367 teaches connecting hoses to the opening from which the spark plug is removed to act as an air intake and exhaust. U.S. Pat. No. 4,070,971 teaches the removal of the pistons altogether.
In an effort to render certain cylinders nonfunctional and yet keep them available for use during heavy load conditions, various push rod, rocker arm and valve devices have been described which may selectively or periodically disable particular cylinders. As noted in U.S. Pat. No. 4,151,817-Mueller the prior art is replete with patents teaching valve disablement.
A few patents have included cam lobe modification in their attempt to solve the fuel waste problem. U.S. Pat. Nos. 2,934,052-Longenecker and 3,277,874-Wagner disclose camshafts with high and low lift lobes for actuating each of the engine valves and means for causing the high or low lift lobe to so activate the valve. In U.S. Pat. No. 2,934,052 an actuating rod is utilized to shift the cam-follower members from one lift lobe to another. The camshaft is taught to be supported by suitable journals mounted in bearings in the engine frame, i.e., the camshaft is axially stationary. U.S. Pat. No. 3,277,874 discloses long and short lift lobe surfaces mounted on an axially stationary camshaft, in conjunction with a fluid operated cam-follower which is positioned at one end of a push rod. The use of modified cam lobes, disposed on an axially displaceable camshaft, to selectively disable cylinders is the subject of my co-pending Patent Application Ser. No. 233,298, filed Feb. 10, 1981.
Fuel efficiency can be optimized, or maximized, by valve timing which reflects the needs and operating conditions of an engine and that which the engine principally "drives", the transmission. A typical four cycle internal combustion engine experiences four unique operating conditions. The first cycle is the intake stroke. As the intake stroke begins, the piston moves from its outermost position inwardly toward the crankshaft. The intake valve opens, and a combustible air-fuel mixture is drawn or sucked into the cylinder. In the compression stroke, the intake port closes and the piston moves outwardly again compressing the air-fuel mixture. At the top of the compression stroke, the spark plug fires and the air-fuel mixture is ignited. Ignition need not take place precisely at the top dead center (TDC) of the stroke, and is typically some degrees before or after TDC, the term degrees referring to rotation of the crankshaft. As the mixture explodes, the piston is driven inwardly, forming the power stroke. Finally, the piston moves outwardly again, as the exhaust port is opened. In the exhaust stroke, the spent products of combustion are ejected from the cylinder. The four cycles are then repeated. In two cycle engines, cycles are combined as is known in the art. Although the principles of this invention will be illustrated in connection with a four cycle engine, they are also applicable to two cycle engines, rotary engines and radial engines. During low speed engine conditions relatively lengthy compression and power strokes will maximize efficiency. During high speed engine conditions relatively lengthy intake and exhaust strokes will maximize efficiency. In a preferred embodiment this invention meets these requirements by providing cam lobes having multiple lift surfaces, the cam lobes being disposed on an axially displaceable cam shaft. During low speed operation a relatively brief amount of lift is transferred through the cam followers for a relatively shorter timed interval to the exhaust and intake valves, and during high speed operation a relatively long amount of lift is provided for a relatively longer timed interval.
Heretofore there has been no suggestion of an internal combustion engine wherein cylinders have cam-activated exhaust and intake ports and cam lobes with multiple lift surfaces shaped to provide selective maintenance of the exhaust and intake ports in an open condition for a plurality of different time periods, wherein the cam lobes are disposed on camshafts capable of axial or longitudinal movement so that the various lift surfaces of the shaped lobes can come to bear in controlling the valves or ports.